The manufacture of tobacco products such as cigarettes is a complicated process.
Typically, tobacco in the form of leaf is received from the farmer and passed to a determined operation in which large stems are removed to produce destemmed tobacco. The destemmed tobacco is packed into bales which are then stored for a suitable time period of up to several years. Following removal from storage, the tobacco bales are fed to a primary processing operation in which the tobacco is removed from the bale, cut into strips and treated to remoisturize the tobacco. Various types of tobacco strip including Burley, Flue Cured and Oriental tobaccos, are blended according to a predetermined recipe. The blended tobacco is then treated by adding various flavorants to provide a cased tobacco which is cut at 20-40 cuts per inch to provide tobacco "cut filler." Various other types of tobacco can be added to the cut filler including puffed tobacco, reconstituted tobacco, tobacco reclaimed from rejected cigarettes, and the like, to provide a final product blend. This blend is then fed to a continuous cigarette rod making apparatus.
During the processing and transport of tobacco filler to the rod-forming unit, certain undesirable impurities and matter foreign to the cigarette can come into contact therewith. The processing sequence therefore include numerous separation steps for the removal of undesirable material. Nevertheless, minute amounts of foreign matter such as pieces of string, plastic wrapping material, paper and the like can be inadvertently incorporated into the tobacco rods and the final cigarette product.
A variety of techniques have been suggested to monitor tobacco or provide quality control of tobacco for undesirable foreign matter. Quality control has usually been accomplished off-line by collecting samples from the factory floor and taking them to a remote site for analysis. The results usually are too late for any significant quality control to be effected. The more typical situation is that the product may be fully manufactured before results are available from the laboratory. Thus, an entire batch of cigarettes may have to be rejected to ensure that it does not have any undesirable impurities or foreign matter therein.
An on-line technique for monitoring tobacco has been suggested in U.S. Pat. No. 4,707,652 to Lowitz which discloses an impurity detector for tobacco utilizing scattered electromagnetic radiation. On or more detectors generate a signal indicating the intensity of the scattered intensity of a normal sample. A change in the output of the detector indicates the presence of an impurity. Such an apparatus is, however, bulky and can be influenced by various extraneous factors such as relative humidity in the manufacture environment, varying amounts of moisture in the tobacco and different types of tobacco in the tobacco blend.
Another on-line technique has been suggested in U.S. Pat. No. 4,839,602 to Pletcher which discloses a device for detecting metal particles in a stream of tobacco. Inductive changes caused by the presence of metal are detected by a detector. The detector generates a signal to the operator indicating the presence of a metallic object.
Other radiation techniques have been suggested for quality control of other difficult to analyze samples or products. U.S. Pat. No. 4,095,696 to Sherwood discloses a produce grader utilizing near infrared (hereinafter "NIR") reflectance technology to distinguish rocks and dirt among fruits and vegetables such as tomatoes or to sort tobacco leaves according to their colors.
The use of NIR reflectance has been suggested for use in quality control of pharmaceuticals for the detection of impurities by Mark et al in Analytical Chemistry, 1985, 57, pp 1449-1456 and in U.S. Pat. No. 4,893,253 to Ladder. Pharmaceuticals are extremely pure and typically have no more than 4 or 5 compounds of relatively uniform particle shape and size, unlike tobacco used in cigarette manufacture which has been reported to have over 2000 compounds and is present in a myriad of different particles of vastly different sizes and shapes.
Because of the chemical and physical diversity of tobacco, the detection of foreign matter, and particularly small particles of organic foreign matter presents an extremely difficult task. Moreover, cigarette manufacturing speeds have recently increased to greater than 6000-7000 cigarettes per minute. Due to these and other factors, there is presently no commercially available system for detecting organic foreign matter hidden within bulk tobacco.